JPH05282663A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent the generation of a head clash by reducing the thickness of the lubricant layer of the magnetic recording medium provided with a magnetic layer and the lubricant layer from the inner peripheral part of tracks toward the outer peripheral part of the tracks. CONSTITUTION:A substrate consisting of Cr is laminated at 200nm by sputtering on a glass substrate 1 and the magnetic layer 3 consisting of CoNiCr is laminated at 50nm thereon; further, a protective layer 4 consisting of C is formed by sputtering at 30nm thickness thereon. A dilute soln. of a lubricant formed by mixing perfluoropolyether as a lubricant with freon serving as a solvent is dropped onto the rotating substrate 1 and the rotating speed of the substrate 1 is changed from 1000rpm to 4000rpm to reduce the thickness of the substrate 1 in a radial direction. The freon is then dried. The thickness of the lubricant layer is made larger in the inner peripheral part of the tracks than the outer peripheral part of the tracks, by which CCS durability is improved over the entire surface of the tracks. The magnetic recording medium which prevents the generation of the backlash of the head and does not generate attraction is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hard type magnetic recording medium for recording and reproducing information with a flying head.

[0002]

2. Description of the Related Art In a hard disk drive for recording and reproducing information on a magnetic recording medium by a flying head, the head and the medium are in a contact friction state when the apparatus is floated or stopped, and the head is floated after the apparatus is started. A contact start / stop method (hereinafter referred to as a CSS method) of transition is adopted.

In the contact friction state at the time of starting and stopping these devices, the friction generated between the head and the medium causes the surface wear damage of the magnetic recording medium. And when the wear damage of the magnetic recording medium reaches the magnetic layer,
Since a so-called head crash phenomenon occurs in which information recorded in the magnetic layer is destroyed, it is an important subject to solve this head crash problem in practical application and improvement of reliability of the magnetic recording medium.

In order to solve the head crash problem, it is necessary to improve the wear resistance of the magnetic recording medium itself. Therefore, the magnetic layer is usually protected by carbon, metal oxides, carbides, nitrides or the like. The layers are overcoated,
Further, as described in Japanese Patent Laid-Open No. 3-71418, for example, a fluorocarbon liquid lubricant is applied on the protective layer to form a liquid lubricant layer.

[0005]

However, the lubricating layer is overcoated on the surface of the protective layer so as to have a uniform thickness, and the wear resistance is constant at any position on the magnetic recording medium. It is produced with the intention. However, when a magnetic recording medium is actually incorporated in a hard disk drive, the relative speed between the head and the magnetic recording medium differs depending on the position of the head in the radial direction of the concentric circle formed by the tracks on the magnetic recording medium, and therefore the predetermined head The time required to reach the peripheral speed required to satisfy the flying height depends on the position of the head on the magnetic recording medium.

That is, compared with the case where the CSS operation is performed in a state where the head is located on the outer peripheral side of the magnetic recording medium,
On the inner circumference side of the magnetic recording medium, the sliding time between the head and the magnetic recording medium until reaching a predetermined flying height becomes longer, and the probability of head crash of the magnetic recording medium becomes higher on the inner circumference side than on the outer circumference side. When the head is in a floating state on the magnetic recording medium, if the head is moved from the outer peripheral side to the inner peripheral side of the magnetic recording medium, the relative speed between the head and the magnetic recording medium decreases, and the flying height of the head increases. Because it decreases
The probability of contact between the head and the magnetic recording medium increases, and the probability of head crash occurrence in the magnetic recording medium is higher on the inner peripheral side than on the outer peripheral side. Especially when the flying height of the head is low at around 2 μ ″ (about 0.05 μm), the probability of head crash of the magnetic recording medium is higher on the inner circumference side than on the outer circumference side.

Further, in order to reduce the probability of head crash occurring on the inner peripheral side of the magnetic recording medium, it is conceivable to increase the thickness of the entire lubricating layer. However, when the thickness of the lubricating layer exceeds a certain value, the coefficient of friction between the head and the medium rapidly increases, and when the thickness of the lubricating layer on the outer peripheral portion of the magnetic recording medium is large, the outer peripheral portion becomes Since the peripheral speed is higher than that of the inner peripheral portion, migration (movement of the lubricating layer) is likely to occur, and therefore adsorption between the head and the outer peripheral portion of the magnetic recording medium is likely to occur.

An object of the present invention is to solve the above-mentioned conventional problems, to provide a magnetic recording medium which has excellent CSS durability over the entire surface of the track, prevents the occurrence of head crash, and prevents the magnetic recording medium from being attracted to the head. To provide.

[0009]

A magnetic recording medium of the present invention which has achieved the above object is a magnetic recording medium in which a magnetic layer made of at least a magnetic material and a lubricating layer are provided on a substrate made of a non-magnetic material. The lubricating layer is characterized in that the thickness of the lubricating layer decreases from the track inner peripheral portion toward the track outer peripheral portion. Here, the fact that the thickness of the lubricating layer decreases from the track inner peripheral portion toward the track outer peripheral portion means that the thickness gradually decreases, and also gradually decreases within a range of a tolerance Δt described later. Including those.

In the magnetic recording medium of the present invention, it is preferable that the lubricating layer on the track has a thickness such that the coefficient of static friction between the head and the magnetic recording medium is 0.5 or less.

Further, in the magnetic recording medium of the present invention, the radius of the innermost track portion is r ₁ , the radius of the outermost track portion is r ₂ , and the thickness of the lubricating layer at the positions r ₁ is t ₁ , r. when the thickness of the lubricant layer at the _second location spaced respectively t _2, the thickness of the lubricant layer at the position of radius _{r (r 1 ≦ r ≦ r} 2) t (r) is of the formula (1) t (r ) = [(T ₁ −t ₂ ) (r ₂ −r) / (r ₂ −r ₁ )] + t ₂ ± Δt (where t ₁ > t ₂ and Δt ≦ t ₂ and Δt is a tolerance) It is preferable to have a distribution represented by (a).

[0012]

In the magnetic recording medium of the present invention, since the thickness of the lubricating layer on the track inner peripheral portion is increased, the CS on the track inner peripheral portion is increased.
The S durability is increased, and the head crash occurrence probability at the track inner peripheral portion is made small, similarly to the head crash occurrence probability at the track outer peripheral portion. Further, since the lubricating layer is thick only in the inner peripheral portion of the track and becomes thinner toward the outer peripheral portion, the occurrence of migration is prevented.

In the magnetic recording medium of the present invention, the lubricating layer on the track has a thickness such that the coefficient of static friction between the head and the magnetic recording medium is 0.5 or less. The rate of occurrence of adsorption of and is further reduced.

Further, the radius of the innermost track of the track is r ₁ ,
When the radius of the outermost track of the track is r ₂ , the thickness of the lubricating layer at r ₁ is t ₁ , and the thickness of the lubricating layer at r ₂ is t ₂ , the radius r (r ₁ ≦ r ≦ r ₂ ) The thickness t (r) of the lubricating layer in the following equation (1) t (r) = [(t ₁ −t ₂ ) (r ₂ −r) / (r ₁ −r ₂ )] + t ₂ ± Δt (Where t ₁ > t ₂ and Δt ≦ t ₂ , where Δt is a tolerance), the magnetic recording medium of the present invention is characterized by having a distribution represented by
Make CSS durability and head crash probability almost equal.

The magnetic recording medium of the present invention is manufactured, for example, as follows. A base layer made of a non-magnetic material is sputtered on a substrate made of a non-magnetic material by 50 to 5
A magnetic layer made of a magnetic material is further laminated to a thickness of 10 to 200 nm on the underlayer. Next, a protective layer having a thickness of 10 to 30 nm is formed on the magnetic layer by sputtering.

Next, CFC 113 (Freon) which is a solvent is mixed with perfluoropolyether used as a lubricant, and the concentration thereof is 0.01 to 0.1 vol%.
After stirring for 3 to 5 minutes to prepare a diluted lubricant solution, the diluted lubricant solution is placed in the solution tank of the dispenser in the spin coater. Next, the substrate provided with the underlayer, the magnetic layer and the protective layer is mounted on a spindle of a spin coater, and the substrate is rotated at a rotation speed of 100 to 1000 rpm.

Next, the position where the lubricant diluted solution was dropped on the substrate mounted on the spin coater was 0.5 to 2 mm away from the outer periphery of the hub that fixed the substrate to the spindle, and the substrate and the dispensing nozzle were separated. Interval 1 to 3
mm, the angle between the substrate and the dispense nozzle is 30
To 60 ° from above, the lubricant diluted solution is dripped onto the substrate. At this time, 1 to 7 kgf / mm in the diluted lubricant solution
^It may be dropped by applying a pressure of ² .

After the lubricant diluted solution is dropped, for example, in FIG.
As in any one of the control patterns shown in B and C, the rotation speed of the spin coater spindle is gradually increased to increase the thickness of the lubricant from the track outer peripheral portion to the track inner peripheral portion, and The freon in the above diluted lubricant solution is dried to obtain a magnetic recording medium having a lubricating layer having a desired shape.

In the magnetic recording medium of the present invention, the substrate is
For example, an Al alloy substrate, a glass substrate, a ceramics substrate or a plastic substrate can be used. Also,
An underlayer may be provided between the substrate and the recording layer, and Cr or the like can be used for the underlayer. The recording layer is, for example, CoNiCr, CoCrTa, or CoPtCr.
Etc. can be used.

A protective layer may be provided on the recording layer, and examples of the protective layer include C, SiO ₂ and ZrO _{2.
-Y 2 O 3, Al 2 O} 3, SiC, TiC, Si
₃ N ₄ , TiN, AlN, carbon such as BN, metal oxides,
Carbides and nitrides can be used. For the lubricating layer, for example, a liquid lubricant such as perfluoropolyether (PFPE) can be used.

[0021]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing a magnetic recording medium according to an embodiment of the present invention. On the glass substrate 1 having a diameter of 65 mm, the underlayer 2 made of Cr is sputtered to form 20 layers.
The magnetic layer 3 made of CoNiCr was laminated on the underlayer 2 to a thickness of 50 nm. Next, a protective layer 4 made of C is deposited on the magnetic layer 3 by sputtering to a thickness of 30n.
m formed.

Next, Freon 113 (Freon) having a purity of 99.9% or more serving as a solvent was mixed with perfluoropolyether having an average molecular weight of about 2500 used as a lubricant, and the concentration thereof was set to 0.03 vol%. After stirring for 5 minutes to prepare a diluted lubricant solution, the diluted lubricant solution was placed in the solution tank of the dispenser in the spin coater. Next, the substrate 1 provided with the underlayer 2, the magnetic layer 3 and the protective layer 4 is mounted on a spindle of a spin coater, the substrate 1 is rotated at a rotation speed of 1000 rpm, and the lubricant diluting solution is placed on the substrate. Was added dropwise.

Substrate 1 mounted on the spin coater at this time
The position where the lubricant diluting solution is dropped is 0.5 mm away from the outer circumference of the hub that fixes the substrate 1 to the spindle, and the distance between the substrate 1 and the dispensing nozzle is 2 m.
m, the angle between the substrate and the dispense nozzle is 60 °
Set to.

After the lubricant diluted solution was dropped, the rotation speed of the spin coater spindle was controlled as shown in B of FIG. 2 (in this embodiment, the rotation speed was changed from 1000 rpm to 2 seconds and then 4000 r).
pm), the thickness of the lubricant was reduced in the radial direction, and Freon in the lubricant diluted solution was dried to prepare a magnetic recording medium of an example having a lubricant layer. The spin coater, dispenser, solution tank, spindle and dispense nozzle are not shown.

After the magnetic recording medium of this example was manufactured, the thickness of the lubricating layer was measured by an ellipsometer. As a result, it was 3.0 n at the innermost track portion (radius r ₁ = 18 mm).
m was 1.0 nm at the outermost periphery of the track (radius r ₂ = 30 mm) and 2.0 nm at the center of the track (radius r ₃ = 24 mm). That is, the thickness t (r ₃ ) of the track center portion (radius r ₃ = 24 mm) is t ₁ = 3.0 nm, t ₂ = 1.0 nm, r _{1 in the} formula (1).
= 30 mm, r ₂ = 18 mm, r ₃ = 24 mm, t (r ₃ ) = 1.0 to 3.0 nm is obtained. However, the thickness distribution of the lubricating layer in this example has an allowable difference. Δt
It can be seen that the equation (1) is satisfied when = 0. Also,
The coefficient of static friction between the magnetic recording medium and the head at each of the above positions was 0.25 at the innermost track portion, the outermost track portion, and the track center portion.

For comparison, a conventional magnetic recording medium was manufactured. FIG. 4 is a cross-sectional view of this magnetic recording medium, in which the underlayer 2, the magnetic layer 3, and the protective layer 4 are sequentially formed on the glass substrate 1 by the same method as in this embodiment shown in FIG. The lubricating layer 5 is formed to have the same thickness, and the lubricating layer 5 is formed on the protective layer 4 by a spin coating method so that the rotation speed of the spindle is 1000 rpm.
And is formed so as to have a uniform thickness at any position on the medium.

After manufacturing the conventional magnetic recording medium, the thickness of the lubricating layer was measured by an ellipsometer. The innermost track (radius r ₁ = 18 mm), the outermost track (radius r ₂ = 30 mm) and the track were measured. Center part (radius r
₃ = 24 mm), all were 1 nm. The coefficient of static friction between the magnetic recording medium and the head at each of the above positions is 0.2 at the innermost track portion, outermost track portion, and track center portion.
It was 5.

A CSS durability test was performed on the magnetic recording medium of the present example produced as described above and the conventional magnetic recording medium. In the CSS endurance test, the magnetic recording medium is incorporated into a hard disk drive device, and the rotation speed is increased to 3600 rpm in 6 seconds and maintained at that rotation speed for 6 seconds as shown in the control pattern shown in FIG. The rotation speed was reduced to 0 rpm and the cycle was stopped for 5 seconds. Then, the number of CSS times until scratches that can be visually confirmed on the medium surface were obtained, and this was defined as the number of CSS durability times.

This CSS endurance test was carried out for the magnetic recording medium of the present example and the conventional magnetic recording medium, respectively, the track innermost portion (radius r ₁ = 18 mm) and the track outermost portion (radius r _2). = 30 mm) and the center of the track (radius r ₃ = 24 mm), and the CSS durability count was determined. Table 1 shows the standardized results.

[0030]

[Table 1]

From these results, in the magnetic recording medium of the conventional example, the CSS endurance number becomes smaller as it gets closer to the inner circumference than the outermost track of the track (r ₂ is 1.0, r ₃ is 0.
9 or less, r ₁ is 0.7 or less), indicating that the inner peripheral portion is inferior in CSS durability to the outer peripheral portion. On the other hand, in the magnetic recording medium of the present embodiment, the CSS at the track outermost portion, the track innermost portion, and the track central portion is set.
The durability is the same ( ₁ for r ₂ , r ₃ and r 1.
0), it was found that the entire surface of the track was excellent in CSS durability.

Further, the magnetic recording medium of the present embodiment does not cause large attraction (for example, attraction having a coefficient of static friction exceeding 0.5) with the head in the hard disk drive device, and the rotation of the magnetic recording medium does not occur. Stop or
The suspension never buckled.

Further, in the magnetic recording medium of the present embodiment, the CSS durability is almost the same over the entire track surface, and the probability of occurrence of head crash is the same at any position, so that the design items of the hard disk drive device can be reduced. This also has the effect of increasing the degree of freedom in design. That is, in the conventional magnetic recording medium, there is a difference in CSS durability between the track inner peripheral portion and the track outer peripheral portion,
Since the head crash occurrence probability differs depending on the position, it is necessary to consider the frequency of track usage so that the track outer circumference side, which has the highest CSS durability, becomes higher.
Although several kinds of design items are required when designing the hard disk drive device, the magnetic recording medium of this embodiment can increase the degree of freedom in designing.

[0034]

As described above, according to the present invention, by making the thickness of the lubricating layer larger in the track inner circumference than in the track outer circumference, the CSS durability is excellent over the entire track and the occurrence of head crash occurs. Prevent, no adsorption occurs,
A magnetic recording medium has been provided which can facilitate the design of a hard disk drive device.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic recording medium of the present invention.

FIG. 2 is a diagram showing a control pattern of a rotational speed of a spindle of a spin coater.

FIG. 3 is a diagram showing a control pattern of a rotation speed of a hard disk drive in a CSS durability test.

FIG. 4 is a sectional view of a conventional magnetic recording medium.

[Explanation of symbols]

 1 Substrate 2 Underlayer 3 Magnetic layer 4 Protective layer 5 Lubricating layer

Claims (3)

[Claims] 1. A magnetic recording medium in which at least a magnetic layer made of a magnetic material and a lubricating layer are provided on a substrate made of a non-magnetic material, and the thickness of the lubricating layer is the track inner peripheral portion. The magnetic recording medium is characterized in that the thickness decreases from the track to the outer periphery of the track. 2. The magnetic recording medium according to claim 1, wherein the lubricating layer on the track has a thickness such that the coefficient of static friction between the head and the magnetic recording medium is 0.5 or less. 3. The radius of the track innermost portion is r ₁ , the radius of the track outermost portion is r ₂ , and the thickness of the lubricating layer at the position r ₁ is t ₁ and the thickness of the lubricating layer at the position r _2. And t ₂ respectively, the thickness t (r) of the lubricating layer at the position of the radius r (r ₁ ≦ r ≦ r ₂ ) is given by the formula (1) t (r) = [(t ₁ −t ₂ ) (R ₂ −r) / (r ₂ −r ₁ )] + t ₂ ± Δt (where t ₁ > t ₂ and Δt ≦ t ₂ , where Δt is a tolerance). The magnetic recording medium according to claim 1 or 2, characterized in that: